1. Field of the Invention
The present invention relates to a horizontal grinding-type rice polishing (milling) machine in which a feeding roller, a grinding roller and a discharging roller are circularly and fixedly installed on a horizontal rotation axis from one end side to the other end side, and the grinding roller is covered with a bran removing screen of concentric cylindrical shape to form a lice polishing room, whereby unpolished rice supplied by the feeding roller is polished in the rice polishing room and discharged from the discharging roller as polished rice.
2. Background Art
A horizontal grinding-type rice polishing machine which is so configured that a feeding roller, (a plurality of) grinding rollers and a discharging roller are circularly and fixedly installed on a horizontal rotation axis from one end side to the other end side, and the grinding roller is covered with a bran removing screen of concentric cylindrical shape to form a rice polishing room, whereby unpolished rice supplied by the feeding roller is polished in the rice polishing room and discharged from the discharging roller as polished rice has been conventionally known in the art.
In the rice polishing machine of the above configuration, unpolished rice is deliver from an unpolished rice hopper and fed into the rice polishing room through a spiral groove formed on the outer periphery of the feeding roller. In the rice polishing room, rice being polished or rice after polished (hereinafter, “rice” in the rice polishing room refers to the rice in mixed state of unpolished rice, rice being polished and rice after polished) is pushed out to the discharging roller as a result of being pushed by the unpolished rice which is successively fed by the feeding roller, and finally pushed into a polished rice outlet from the discharging roller.
It is requested that polishing degree of polished rice is adjusted in accordance with the intended polishing degree, and in accordance with the type of the rice, and the polishing degree can be adjusted by changing the residence time, the loading amount and the passage in the rice polishing room.
As a means for appropriately setting the residence time and loading amount in the rice polishing room, a stopper for restricting passage by preventing flow of the rice or a flap for controlling the flow rate is conventionally provided along the inner peripheral surface of the bran removing screen. The stopper is fixedly provided on the inner peripheral surface of the bran removing screen so as to make the gap with respect to the grinding roller extremely small thereby preventing the rice from flowing and guiding the rice to the region where a stopper is not provided, and thus restricting the passage. The flap narrows the gap with respect to the grinding roller to some degree, thereby controlling the flow rate of the rice in the gap. That is, according to the conventional measure, the loading amount and the flow rate (residence time) of the rice in the rice polishing room are adjusted by making the flap variable or enabling manual changing of its angle by an operator.
However, such a variable-type flap applied along the circumferential direction of the bran removing screen cannot be so long. That is, such a flap cannot be effective along the substantially entire circumference of the bran removing screen, so that there is a limitation in equalizing distribution of rice in the rice polishing room. This made the structure of the bran removing screen complicated.
Also, though a structure in which a fixed-type flap is fixedly provided on the inner peripheral surface of the bran removing screen in the same manner as the stopper is also adopted in combination with the variable flap, since the bran removing screen itself is essentially fixedly provided and cannot be modulated in accordance with the type of the rice or the intended polishing degree, the position of the fixed-type flap is also fixed and there is a case that a desired polishing degree cannot be achieved.
As another means for adjusting the polishing degree, a structure of adjusting free opening of an outlet of polished rice is known. That is, at an outlet of polished rice, a shutter having a pushing force against the flow direction of polished rice is provided, and free opening of the shutter is adjusted. The narrower the free opening, the higher the polishing degree becomes because of increase of the residence time in the rice polishing room.
However, if the free opening is controlled as described above, the polishing efficiency is deteriorated on the other hand. That is, as a result of decreasing the discharge amount of the polished rice per unit time, longer time is required for obtaining the intended amount of polished rice.
Yet another problem associated with the conventional horizontal grinding-type rice polishing machine is that since the spiral groove of the feeding roller is formed as one groove from the initial end surface to the terminal end surface of the roller, the pressure of the unpolished rice to be discharged into the rice polishing room from the outlet end of the groove concentrates at one point under rotation, and rotation of the pressure concentrated point may cause vibration of axial center of the rotation axis. Furthermore, in association with that the degree of pressure application on the rice polishing room in one rotation varies depending on arrangement of the stopper and flap provided nearest to the inlet in the rice polishing room and opposing to the terminal end surface of the feeding roller, vibration occurs in the grinding roller, which results in unequal rice polishing or adversely affects on the durability of parts.
Furthermore, in assembling the grinding roller and discharging roller on the rotation axis, the assembly is proceeded in the manner that first the feeding roller is assembled on the rotation axis while cantilevering the inlet end side of the rotation axis, and thereafter the center hole of each grinding roller is passed on the rotation axis to be slid to a predetermined position in sequence. However, as the grinding rollers are assembled to the rotation axis, the part of the outlet side end is downwardly inclined because of the weight of the grinding rollers. This causes the assembled grinding rollers to slide toward the outlet side end and come off, and also causes a trouble in assembling additional grinding roller to a predetermined position.